HPS 420 Final Exam With Complete
Solutions
Direct ionization vs. Indirect ionization (1) - ANSWER direct: All charged particles that
directly disrupt atomic structures of any material through which they pass causing
chemical or biologic effects.
indirect: Does not directly produce damage themselves; it produces fast-moving
particles when they interact with material. Secondary particles then go on to cause
biologic damage (e- to move out)
Direct ionization is associated with?
Indirect action is associated with? (1) - ANSWER direct: Particulate Radiation (alpha
particles, electrons, protons, heavy charged particles)
indirect: Electromagnetic Radiation (X- and Y-Ray)
(Neutrons also use INDIRECT IONIZATION)
Direct vs. Indirect action (1) - ANSWER Direct: the atoms of the target itself may be
ionized or excited thus the initializing the chain of events that leads to a biological
change. dominant for densely ionizing radiation (=high LET radiation = alpha particles or
neutrons or protons)
Indirect: When H20 or other molecules are ionized. These free radicals act as
intermediaries to cause damage. Secondary electron interacts with a water molecule to
produce (OH-) which causes damage to DNA; occurs with Electromagnetic radiation
How do X-rays and neutrons differ? (1) - ANSWER X-rays interact with electrons of an
atom, while neutrons interact with the nuclei of an atom. This results in recoil protons
and is associated with Spallation
Photoelectric effect: what is it and what energy range they dominate (ch 1) - ANSWER
the photon is absorbed, knocks out an electron in the K shell of the atom (inner shell)
1-10 keV low
photo energies completely absorbed knocks out electron
compton scattering: what is it and what energy range they dominate (ch 1) - ANSWER
Interaction of an x-ray photon with a loosely bound outer shell electron of an atom
- some incident photon energy is transferred to the electron (minus binding energy of
,the electron
- scattered photon continues with less energy in a different direction
- over all energies, peaking midrange at 10 KeV - 10MeV
Pair production: what is it and what energy range they dominate (ch 1) - ANSWER The
incident photon spontaneously converts into an electron and a positron which then
deposit any remaining energy in the medium through Coulomb interactions
- only occur is E > 1.022 MeV
- not seen in diagnostic imaging
excitation vs. ionization (ch 1) - ANSWER excitation: Raising of an electron in an atom or
molecule to a higher energy level without actual ejection of the electron. transfers
enough energy to an orbital electron to displace it further away from the nucleus.
ionization: The electron is ejected resulting in an ion pairone freed electionand the
remaining atom
Understand the wave model and how wavelength, frequency and velocity are related (ch
1) - ANSWER wave model: electromagnetic radiation is a self propagating wave with
electric and magnetic components ( perpendicular)
- wavelength x frequency = velocityV×f=c
Particle model: describes electromagnetic radiation os thought of as a stream of
separate particles or photons
- energy = planks constant x frequencyE=h×v
Know the two major DSB repair pathways and how they differ. (ch 2) - ANSWER 1.
Homologous recombination repair (HRR)
- uses a template to repair the damage done to the genome
- most faithful
- only during S phase and G2 phase
2. Nonhomologous end joining (NHEJ)
- prevents cell from continuing the cell cycle until fully repaired, joining the end free
ends of the strand
- no template, no dna copy
- least faithful
- All cell cycles predominate in G1
,Understand the various types of aberrations and how irradiation in a particular cell
cycle may lead to particular types of aberrations (ch 2) - ANSWER 1. Chromatid
aberration: Occurs after irradiation in S or G2 where only one chromatid is involved
2. Chromasome aberration: G1 irradiation where both sister chromatids are involved
what are the three types of lethal aberrations - ANSWER Dicentric, Ring, and anaphase
bridge
how are dicentric aberrations formed - ANSWER irradiation in G1 with two breaks in the
chromatid, the formed ring of the centric ring that has now duplicated
chromosomal, lethal, asymmetrical
how are ring aberrations formed - ANSWER radiation in G1 where two breaks have
occurred, the chromatid closes on itself and forms a ring while two fragments have
broken off chromosomal, lethal, asymmetrical
how are fragment aberrations formed - ANSWER radiation in G1 with two breaks that
occurred, a result from ring or interstitial deletion where parts of the DNA are parted out
and either fade away or attempt to form smaller rings or small chromosomes
Know the difference between symmetrical and asymmetrical aberrations (ch 2) -
ANSWER symmetrical: balanced gene rearrangements
no cell death
both have centromeres
transportation abberation
stable
asymmetrical:
not balanced gen rearrangements where fragment is usually lost
death or loss of DNA
has 1 or no centromere
dicentric and fragment abberations
unstable
Know what mathematical function chromosome aberrations follow at low and high
doses (ch 2) - ANSWER
what are the different staining methods used for detecting chromosome aberrations (ch
2) - ANSWER 1. Giemsa staining
, 2. G-banding
3. Fluorescence in situ hybridization (FISH)
4. MFISH
5. MBAND
Giesma stain - ANSWER a stain that binds to adenine-thymine to visualize
chromosomes.
Good for visualizing dicentrics, rings, and fragments.
What is G-banding - ANSWER stain with giemsa and add trypsin solution to "eat" away
areas causing a defined banding pattern- good for seeing deletions in chromosomes
What is flourescence in-situ hybridization (FISH) - ANSWER fluorescent probes that bind
to specific chromosomes usually 1-3 at a time
What is MFISH - ANSWER a more indepth version of FISH that allows each chromosome
to be "painted" with a specific color
What is MBAND - ANSWER allows for a single chromosome to be "painted" with bands
for specific segments of the chromosome
Understand what the plating efficiency is and why it is needed (ch 3) - ANSWER the
capability of a single cell to grow into a large colony
PE: (number of colonies/ number of cells plated) x 100
SF: number of colonies/ number of cells plated x (PE/100)
Know the components of the linear quadratic model (ch 3)
- α/β ratio and its significance
- what type of damage do the α and β components represent - ANSWER it is the dose at
which linear and quadratic components of cell killing are equal
Solutions
Direct ionization vs. Indirect ionization (1) - ANSWER direct: All charged particles that
directly disrupt atomic structures of any material through which they pass causing
chemical or biologic effects.
indirect: Does not directly produce damage themselves; it produces fast-moving
particles when they interact with material. Secondary particles then go on to cause
biologic damage (e- to move out)
Direct ionization is associated with?
Indirect action is associated with? (1) - ANSWER direct: Particulate Radiation (alpha
particles, electrons, protons, heavy charged particles)
indirect: Electromagnetic Radiation (X- and Y-Ray)
(Neutrons also use INDIRECT IONIZATION)
Direct vs. Indirect action (1) - ANSWER Direct: the atoms of the target itself may be
ionized or excited thus the initializing the chain of events that leads to a biological
change. dominant for densely ionizing radiation (=high LET radiation = alpha particles or
neutrons or protons)
Indirect: When H20 or other molecules are ionized. These free radicals act as
intermediaries to cause damage. Secondary electron interacts with a water molecule to
produce (OH-) which causes damage to DNA; occurs with Electromagnetic radiation
How do X-rays and neutrons differ? (1) - ANSWER X-rays interact with electrons of an
atom, while neutrons interact with the nuclei of an atom. This results in recoil protons
and is associated with Spallation
Photoelectric effect: what is it and what energy range they dominate (ch 1) - ANSWER
the photon is absorbed, knocks out an electron in the K shell of the atom (inner shell)
1-10 keV low
photo energies completely absorbed knocks out electron
compton scattering: what is it and what energy range they dominate (ch 1) - ANSWER
Interaction of an x-ray photon with a loosely bound outer shell electron of an atom
- some incident photon energy is transferred to the electron (minus binding energy of
,the electron
- scattered photon continues with less energy in a different direction
- over all energies, peaking midrange at 10 KeV - 10MeV
Pair production: what is it and what energy range they dominate (ch 1) - ANSWER The
incident photon spontaneously converts into an electron and a positron which then
deposit any remaining energy in the medium through Coulomb interactions
- only occur is E > 1.022 MeV
- not seen in diagnostic imaging
excitation vs. ionization (ch 1) - ANSWER excitation: Raising of an electron in an atom or
molecule to a higher energy level without actual ejection of the electron. transfers
enough energy to an orbital electron to displace it further away from the nucleus.
ionization: The electron is ejected resulting in an ion pairone freed electionand the
remaining atom
Understand the wave model and how wavelength, frequency and velocity are related (ch
1) - ANSWER wave model: electromagnetic radiation is a self propagating wave with
electric and magnetic components ( perpendicular)
- wavelength x frequency = velocityV×f=c
Particle model: describes electromagnetic radiation os thought of as a stream of
separate particles or photons
- energy = planks constant x frequencyE=h×v
Know the two major DSB repair pathways and how they differ. (ch 2) - ANSWER 1.
Homologous recombination repair (HRR)
- uses a template to repair the damage done to the genome
- most faithful
- only during S phase and G2 phase
2. Nonhomologous end joining (NHEJ)
- prevents cell from continuing the cell cycle until fully repaired, joining the end free
ends of the strand
- no template, no dna copy
- least faithful
- All cell cycles predominate in G1
,Understand the various types of aberrations and how irradiation in a particular cell
cycle may lead to particular types of aberrations (ch 2) - ANSWER 1. Chromatid
aberration: Occurs after irradiation in S or G2 where only one chromatid is involved
2. Chromasome aberration: G1 irradiation where both sister chromatids are involved
what are the three types of lethal aberrations - ANSWER Dicentric, Ring, and anaphase
bridge
how are dicentric aberrations formed - ANSWER irradiation in G1 with two breaks in the
chromatid, the formed ring of the centric ring that has now duplicated
chromosomal, lethal, asymmetrical
how are ring aberrations formed - ANSWER radiation in G1 where two breaks have
occurred, the chromatid closes on itself and forms a ring while two fragments have
broken off chromosomal, lethal, asymmetrical
how are fragment aberrations formed - ANSWER radiation in G1 with two breaks that
occurred, a result from ring or interstitial deletion where parts of the DNA are parted out
and either fade away or attempt to form smaller rings or small chromosomes
Know the difference between symmetrical and asymmetrical aberrations (ch 2) -
ANSWER symmetrical: balanced gene rearrangements
no cell death
both have centromeres
transportation abberation
stable
asymmetrical:
not balanced gen rearrangements where fragment is usually lost
death or loss of DNA
has 1 or no centromere
dicentric and fragment abberations
unstable
Know what mathematical function chromosome aberrations follow at low and high
doses (ch 2) - ANSWER
what are the different staining methods used for detecting chromosome aberrations (ch
2) - ANSWER 1. Giemsa staining
, 2. G-banding
3. Fluorescence in situ hybridization (FISH)
4. MFISH
5. MBAND
Giesma stain - ANSWER a stain that binds to adenine-thymine to visualize
chromosomes.
Good for visualizing dicentrics, rings, and fragments.
What is G-banding - ANSWER stain with giemsa and add trypsin solution to "eat" away
areas causing a defined banding pattern- good for seeing deletions in chromosomes
What is flourescence in-situ hybridization (FISH) - ANSWER fluorescent probes that bind
to specific chromosomes usually 1-3 at a time
What is MFISH - ANSWER a more indepth version of FISH that allows each chromosome
to be "painted" with a specific color
What is MBAND - ANSWER allows for a single chromosome to be "painted" with bands
for specific segments of the chromosome
Understand what the plating efficiency is and why it is needed (ch 3) - ANSWER the
capability of a single cell to grow into a large colony
PE: (number of colonies/ number of cells plated) x 100
SF: number of colonies/ number of cells plated x (PE/100)
Know the components of the linear quadratic model (ch 3)
- α/β ratio and its significance
- what type of damage do the α and β components represent - ANSWER it is the dose at
which linear and quadratic components of cell killing are equal
